Bones, muscles, glands, and even the brain can function without immediate danger if they fail, but the kidneys are critical. If kidney function fails, the functions of bones, muscles, and the brain cannot be maintained. The timing of starting dialysis for patients with chronic kidney disease is an important decision with implications for patients' lives and costs. Guidelines recommend considering starting dialysis when the weekly kidney clearance of urea falls below 2.0, unless the patient's weight is stable and they lack symptoms of kidney failure.